Fuel injection valve

ABSTRACT

A valve seat member has a valve seat with a fuel injection aperture. A valve body is movable between a close position wherein the valve body is put on the valve seat and an open position wherein the valve body is separated from the valve seat. A biasing member biases the valve body in a direction of the close position. An electromagnetic coil, upon energization, moves the valve body in a direction of the open position against the biasing force of the biasing member. A nozzle plate is connected to the valve seat member in a manner to cover the fuel injection aperture. The nozzle plate has at a part thereof facing the fuel injection aperture a domed portion that is projected away from the fuel injection aperture. The domed portion has a plurality of fuel injection openings. A side wall extends around and along a periphery of the nozzle plate so as to form a fuel holding recess that is defined by the nozzle plate other than domed portion and the side wall. The fuel holding recess is able to hold a certain amount of a fuel by the force of a surface tension possessed by the fuel.

BACKGROND OF THE INVENTION

1. Field of the Invention

The present invention relates to fuel injection valves for internalcombustion engines.

2. Description of the Related Art

Hitherto, various fuel injection valves for internal combustion engineshave been proposed and put into practical use. One of them is shown inJapanese Laid-open Patent Application (Tokkaihei) 10-122085, whichgenerally comprises a seat member with a fuel injection opening, a valveproper movable in a direction to selectively close and open the fuelinjection opening, a biasing means for biasing the valve proper in adirection to close the aperture and an electromagnetic coil that, whenenergized or in ON condition, lifts the valve proper from the seatmember to open the opening. Thus, in response to ON/OFF condition of theelectromagnetic coil, a fuel injection through the fuel injectionopening is effected and stopped continuously.

SUMMARY OF THE INVENTION

However, due to inherent construction, some of the fuel injection valvesof the above-mentioned type have the following drawbacks. That is, longusage of the fuel injection valve tends to produce a fuel compositiondeposit at a peripheral area of the fuel injection opening. Such deposithas an undesired effect on the fuel injection performance, particularlyon the fuel injection rate and fuel mist shaping.

It is therefore an object of the present invention to provide a fuelinjection valve which is free of the above-mentioned drawback.

In accordance with a first aspect of the present invention, there isprovided a fuel injection valve which comprises a valve seat memberhaving a valve seat with a fuel injection aperture; a valve body that ismovable between a close position wherein the valve body is put on thevalve seat and an open position wherein the valve body is separated fromthe valve seat; a biasing member that biases the valve body in adirection of the close position; an electromagnetic coil that, uponenergization, moves the valve body in a direction of the open positionagainst the biasing force of the biasing member; a nozzle plateconnected to the valve seat member in a manner to cover the fuelinjection aperture, the nozzle plate having at a part thereof facing thefuel injection aperture a domed portion that is projected away from thefuel injection aperture, the domed portion having a plurality of fuelinjection openings; and a side wall that extends around and along aperiphery of the nozzle plate so as to form a fuel holding recess thatis defined by the nozzle plate other than domed portion and the sidewall, the fuel holding recess being able to hold a certain amount of afuel by the force of a surface tension possessed by the fuel.

In accordance with a second aspect of the present invention, there isprovided a fuel injection valve which comprises a cylindrical valve seatmember having a valve seat with a fuel injection aperture; a valve bodyhaving a valve ball, the valve ball being movable between a closeposition wherein the valve ball is put on the valve seat and an openposition wherein the valve ball is separated from the valve seat; abiasing member that biases the valve ball of the valve body in adirection of the close position; an electromagnetic coil that, uponenergization, moves the valve ball of the valve body in a direction ofthe open position against the biasing force of the biasing member; acircular nozzle plate connected to the cylindrical valve seat member ina manner to cover the fuel injection aperture, the circular nozzle platehaving at a center part thereof facing the fuel injection aperture adomed portion that is projected away from the fuel injection aperture,the domed portion having a plurality of fuel injection openings; and acylindrical side wall that extends around and along a periphery of thecircular nozzle plate so as to form a fuel holding recess that isdefined by the circular nozzle plate other than domed portion and thecylindrical side wall, the fuel holding recess being able to hold acertain amount of a fuel by the force of a surface tension possessed bythe fuel.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects and advantages of the present invention will becomeapparent from the following description when taken in conjunction withthe accompanying drawings, in which:

FIG. 1 is a sectional view of a fuel injection valve of the presentinvention;

FIG. 2 is an enlarged sectional view of an essential potion of the fuelinjection valve of the present invention;

FIG. 3 is a much enlarged sectional view of a nozzle end portion of thefuel injection valve of the present invention; and

FIG. 4 is a much enlarged but partial view of a circular nozzle plateemployed in the fuel injection valve of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following, a fuel injection valve 100 of the present inventionwill be described in detail with reference to the accompanying drawings.

For ease of understanding, various directional terms such as right,left, upper, lower, rightward and the like will be used in the followingdescription. However, such terms are to be understood with respect toonly the drawing or drawings on which a corresponding portion or part isshown.

Referring to FIG. 1, there is shown in a sectional manner an entireconstruction of the fuel injection valve 100 of the present invention.

As shown, fuel injection valve 100 generally comprises a magnetic metaltube 3, a plastic casing 2 covering magnetic metal tube 3, a metal coretube 5 received in a lower portion of metal tube 3, a metal yoke member13 arranged to surround core tube 5 through metal tube 3, and a plasticcover 16 embedded in plastic casing 2.

Magnetic metal tube 3 is produced by pressing a magnetic stainlesssteel. As is shown, magnetic metal tube 3 comprises a larger diameterupper portion 3 a and a smaller diameter lower portion 3 b which areconnected through a tapered center portion (no numeral). Although notshown in the drawing, in practical use, an upper end of magnetic metaltube 3 is received in a boss part of a fuel piping so that a fuel is fedto an interior 4 of metal tube 3.

Disposed about an upper end of metal tube 3 is an O-ring 18 by which ahermetical sealing between the upper end of metal tube 3 and the bosspart of the fuel piping is achieved.

Disposed in the upper end of metal tube 3 is an injection molded filterunit 21 that comprises an annular metal core 21 a, a cylindrical plasticframe 21 b held by metal core 21 a and a mesh member 21 c held by frame21 b. Preferably, plastic frame 21 b is made of soft plastic material,such as fluorine plastic, Nylon (Trade name) or the like which is softerthan magnetic metal tube 3. Due to provision of mesh member 21 c, thefuel is filtered before flowing into the interior 4 of metal tube 3 fromthe fuel piping. As shown, metal core tube 5 is concentrically receivedin smaller diameter lower portion 3 b of metal tube 3. As will becomeapparent as the description proceeds, metal core tube 5 functions toform a closed loop magnetic path for an electromagnetic coil 15 incooperation with an anchor portion 10 a of a valve body 9 and yokemember 13. Furthermore, metal core tube 5 has another function tocontrol or adjust an open position of valve body 9. In the illustratedembodiment, metal core tube 5 is press-fitted in metal tube 3 leaving apredetermined small clearance “67” between an upper end of anchorportion 10 a of valve body 9 and a lower end of metal core tube 5.

As is best seen from FIG. 2, in a lower end of magnetic metal tube 3,more specifically, in a lower end of smaller diameter lower portion 3 bof metal tube 3, there is tightly installed a cylindrical valve seatmember 7. In the illustrated embodiment, cylindrical valve seat member 7is secured to metal tube 3 by means of welding.

Valve seat member 7 has a generally conical bore with a valve seat 7 aon which a valve ball 11 is operatively put. Valve seat member 7 hasfurther at a lower end thereof a fuel injection aperture 7 b from whichthe fuel is injected outward, that is, downward in the drawing. That is,when valve ball 11 is put on valve seat 7 a as shown in the drawing,fuel injection valve 100 assumes its OFF or close position, while whenvalve ball 11 is lifted from valve seat 7 a, fuel injection valve 100assumes its ON or open position, as will become apparent as thedescription proceeds.

As best seen from FIG. 2, fuel injection aperture 7 b of valve seatmember 7 is covered with a circular nozzle plate 8 that is secured to aleading end surface of valve seat member 7 by means of welding. Asshown, circular nozzle plate 8 generally comprises an annular baseportion 8 a that is secured to the leading end surface of valve seatmember 7 and a domed center portion 8 b that actually covers fuelinjection aperture 7 b of valve seat member 7. Domed center portion 8 bis projected in a direction away from fuel injection aperture 7 b.

As is seen from FIG. 3, domed center portion 8 b is formed with aplurality of injection openings 8 c. The detail of the circular nozzleplate 8 will be described hereinafter.

As is seen from FIGS. 2 and 3, between metal core tube 5 and valve seatmember 7, there is arranged the above-mentioned valve body 9 that isaxially movable in smaller diameter lower portion 3 b of metal tube 3.As is mentioned hereinabove, valve body 9 is constructed of a magneticmetal material and comprises a larger diameter anchor upper portion 10 aand a smaller diameter tubular lower portion 10 b. Upper portion 10 a ofvalve body 9 is formed with a cylindrical bore 10 c into which a lowerend of a coil spring 12 is received, and smaller diameter tubular lowerportion 10 b of valve body 9 has a leading end secured to valve ball 11by means of welding.

As is seen from FIG. 1, coil spring 12 has an upper end seated on alower end of a cylindrical adjuster member 19 received in metal coretube 5. Although not well shown in the drawing, adjuster member 19 has athreaded outer surface engaged with a threaded inner surface of metalcore tube 5, so that turning adjuster member 19 about its axis cancontrol or adjust the biasing force produced by coil spring 12. It is tobe noted that due to the biasing force of coil spring 12, valve body 9is biased to press valve ball 11 thereof against valve seat 7 a of valveseat member 7, that is, in a direction to close fuel injection aperture7 b.

As is described hereinabove, around smaller diameter lower portion 3 bof magnetic metal tube 3, there is arranged metal yoke member 13 whichis cylindrical in shape. In the illustrated embodiment, a press fittingis used for securing yoke member 13 to smaller diameter lower portion 3b of magnetic metal tube 3.

As is seen from FIG. 1, between yoke member 13 and smaller diameterlower portion 3 b of magnetic metal tube 3, there is arranged aconnecting core 14 which is a generally C-shaped magnetic metal memberput around the smaller diameter lower portion 3 b.

Furthermore, between yoke member 13 and smaller diameter lower portion 3b of magnetic metal tube 3, there is concentrically arranged theabove-mentioned electromagnetic coil 15. This coil 15 comprises acylindrical plastic bobbin 15 a concentrically disposed about smallerdiameter lower portion 3 b of metal tube 3 and a coil proper 15 b woundon bobbin 15 a. Electromagnetic coil 15 is connected to a power source(not shown) through wires 20 a embedded in both plastic cover 16 andplastic casing 2 and pins 20 b installed in a connector part 17. Asshown, connector part 17 is integral with plastic casing 2.

As is understood from FIG. 1, plastic cover 16 is partially put on theouter surface of magnetic metal tube 3. It is to be noted that yokemember 13, connecting core 14 and electromagnetic coil 15 are integrallyassembled when plastic cover 16, plastic casing 2 and connector part 17are molded by means of injection molding.

In OFF condition wherein electromagnetic coil 15 is not energized, valveball 11 of valve body 9 is pressed against valve seat 7 a of valve seatmember 7 due to the biasing force of coil spring 12. Thus, in thiscondition, fuel injection aperture 7 b of fuel injection valve 100 isclosed.

As is seen from FIG. 1, in the close condition of valve 100, there isdefined the clearance “δ” between an upper end of anchor portion 10 a ofvalve body 9 and a lower end of metal core tube 5.

While, when electromagnetic coil 15 is energized, metal core tube 5,anchor portion 10 a and yoke member 13 constitute a closed magneticcircuit, and thus, to anchor portion 10 a, there is applied a magneticforce in a direction to pull it 10 a toward metal core tube 5. Since inthis condition the magnetic force thus produced is larger than thebiasing force produced by coil spring 12, valve body 9 is pulled towardcore tube 5 separating valve ball 11 of valve body 9 from valve seat 7 aof valve seat member 7. Thus, in this condition, fuel injection aperture7 b of fuel injection valve 100 is opened.

As will be understood from FIGS. 1 and 2, in the open condition of fuelinjection valve 100, pressurized fuel in the interior 4 of magneticmetal tube 3 is forced to run through the center passage of adjustermember 19, cylindrical bore 10 c of valve body 9, windows 9 a formed insmaller diameter tubular lower portion 10 b of valve body 9, a backpressure chamber 6 defined between smaller diameter lower portion 10 band magnetic metal tube 3 and a certain clearance defined between valveball 11 and valve seat 7 a and injected outward, that is, downward inthe drawings, from fuel injection aperture 7 b of valve seat member 7,more specifically, from fuel injection openings 8 c (see FIG. 3) ofcircular nozzle plate 8 that covers fuel injection aperture 7 b.

In the following, important features of the present invention will bedescribed in detail with reference to the drawings, particularly FIG. 3.

As is well shown in FIG. 3 and is described hereinabove, circular nozzleplate 8 comprises an annular base portion 8 a that is secured to theleading end surface of valve seat member 7, a domed center portion 8 bthat actually covers fuel injection aperture 7 b of valve seat member 7and a plurality of injection openings 8 c that are formed in domedcenter portion 8 b.

As is seen from FIG. 3, smaller diameter lower portion 3 b of magneticmetal tube 3 has a lower end part 3 b′ that projects downward beyondcircular nozzle plate 8 by a certain degree. With this, as is indicatedby a shadowed zone, there is formed a so-called fuel holding recess “G”which is defined by a lower surface of annular base portion 8 a ofcircular nozzle plate 8 and an inner surface 3 c of lower end part 3 b′of magnetic metal tube 3. That is, fuel holding recess “G” isconstructed to hold a certain amount of fuel by the force of a surfacetension possessed by the fuel.

It is to be noted that due to the projected shape of domed centerportion 8 b, fuel injection openings 8 c formed in domed center portion8 b are prevented from being covered by the fuel contained in fuelholding recess “G”. As is known, such domed center portion 8 b can beeasily produced by pressing a spherical had member against a metalplate.

As is seen from FIG. 3, the thickness of fuel contained in fuel holdingrecess “G” increases with increase of a distance from the annularperiphery of domed center portion 8 b. This means that fuel injectionopenings 8 c are positioned away from the area where a larger amount offuel is contained, which minimizes the possibility of covering fuelinjection openings 8 c with the residual fuel on circular nozzle plate8. In other words, fuel injection openings 8 c are suppressed fromhaving the undesired fuel composition deposit.

In order to find out the optimum shape of fuel holding recess “G”, thatis, in order to minimize the possibility of covering fuel injectionopenings 8 c with a residual fuel on circular nozzle plate 8, theinventor carried out various examinations and finally found the optimumshape, which is substantially defined by a diameter “D1” of domed centerportion 8 b of circular nozzle plate 8, an inner diameter “D2” of lowerend part 3 b′ of magnetic metal tube 3, a height “h” of domed centerportion 8 b and a height “H” of lower end part 3 b′. As is seen fromFIG. 3, the height “H” is the length from a peripheral end of circularnozzle plate 8 to the leading end of lower end part 3 b′.

The examinations carried out by the inventor will be described in thefollowing.

Examination-1

Various samples of the fuel injection valve that are different in shape(viz., “D1” and “h”) of domed center portion 8 b of circular nozzleplate 8 were prepared and subjected to a fuel injection operation usingan internal combustion engine.

According to this Examination, the inventor found that when domed centerportion 8 b of the fuel injection valve satisfies the followingdimensional condition, fuel injection openings 8 c of domed centerportion 8 b are suppressed from having the undesired fuel compositiondeposit.

That is:1.5 mm≦D1≦2.5 mm  (1)and0.1 mm≦h  (2)

Actually, when domed center portion 8 b did not satisfy theabove-mentioned dimensional condition (viz., (1) and (2)), some of thesamples showed a certain fuel composition deposit on a peripheral areaof fuel injection openings 8 c.

In view of the above, the inventor has the following consideration forthe dimensional condition of domed center portion 8 b of circular nozzleplate 8 installed in the fuel injection valve.

If the diameter “D1” is too small, fuel holding recess “G” thus producedhas a center portion thereof advanced largely to a center area of domedcenter portion 8 b, which increases the possibility of covering some offuel injection openings 8 c of domed center portion 8 b with a residualfuel. While, if the diameter “D1” is too large, the distance between theperiphery of domed center portion 8 b of circular nozzle plate 8 and theinner surface 3 c of lower end part 3 b′ of magnetic metal tube 3becomes very short, which reduces the bottom area of fuel holding recess“G” causing increase in height of the recess “G” and thus increasing thepossibility of covering some of fuel injection openings 8 c with theresidual fuel. Furthermore, if the height “h” is too small, thepossibility of covering some of fuel injection openings 8 c with theresidual fuel is increased.

Examination-2

Like the above, various samples of the fuel injection valve that aredifferent in shape (viz., “D1” and “D2”) of annular base portion 8 a ofcircular nozzle plate 8 were prepared and subjected to a fuel injectionoperation using the internal combustion engine.

According to this Examination, the inventor found that when annular basepotion 8 a of the fuel injection valve satisfies the followingdimensional condition, fuel injection openings 8 c of domed centerportion 8 b are suppressed from having the undesired fuel compositiondeposit.

That is:(D2−D1)/2≧1.25 mm  (3)

Actually, when annular base portion 8 a did not satisfy theabove-mentioned dimensional condition (viz., (3)), some of the samplesshowed a certain fuel composition deposit on a peripheral area of fuelinjection openings 8 c.

In view of the above, the inventor has the following consideration forthe dimensional condition of annular base portion 8 a of circular nozzleplate 8 installed in the fuel injection valve.

If the value “(D2−D1)/2” is too small, that is, if the distance betweenthe periphery of domed center portion 8 b of circular nozzle plate 8 andinner surface 3 c of lower end part 3 b′ of magnetic metal tube 3 is toosmall, that is, smaller than 1.25 mm, the bottom area of fuel holdingrecess “G” is reduced which causes increase in height of the recess “G”and thus increases the possibility of covering some of fuel injectionopenings 8 c with the residual fuel. The dimensional condition of (3)means that fuel holding recess “G” should be located near the lower endpart 3 b′ of magnetic metal tube 3.

Examination-3

Like the above, various samples of the fuel injection valve that aredifferent in size (viz., “H”) of lower end part 3 b′ of magnetic metaltube 3 were prepared and subjected to a fuel injection operation usingthe internal combustion engine.

According to this Examination, the inventor found that when lower endpart 3 b′ of the fuel injection valve satisfies the followingdimensional condition, fuel injection openings 8 c of domed centerportion 8 b are suppressed from having the undesired fuel compositiondeposit.

That is:H≦2.0 mm  (4)

Actually, when lower end part 3 b′ did not satisfy the above-mentioneddimensional condition (viz., (4)), some of the samples showed a certainfuel composition deposit on a peripheral area of fuel injection openings8 c.

In view of the above, the inventor has the following consideration forthe dimensional condition of lower end part 3 b′ of magnetic metal tube3 installed in the fuel injection valve.

If the height “H” is too large, a fuel trapping by lower end part 3 b′becomes remarkable and thus an actual capacity of fuel holding recess“G” is increased, which increases the possibility of covering some offuel injection openings 8 c of domed center portion 8 b with theresidual fuel.

As a result of the above-mentioned three Examinations, the inventornoted that if the fuel injection valve satisfies all of theabove-mentioned dimensional conditions, that is, (1), (2), (3) and (4),the valve would show the best performance in suppressing formation ofundesired fuel composition deposit on the peripheral area of fuelinjection openings 8 c.

FIG. 4 shows an advantage expected by the present invention when a smallvolume of fuel holding recess “G” is produced at a bent border portionbetween domed center portion 8 b and annular base portion 8 a. As isunderstood from this drawing, in such case, an annular recess defined bythe bent border portion can serve as a container for the fuel, and thus,fuel injection openings 8 c of domed center portion 8 b are suppressedfrom being covered with the fuel, which suppresses or at least minimizesthe possibility of having the undesired fuel composition deposit on theperipheral area of fuel injection openings 8 c.

As is described hereinabove, in the fuel injection valve of the presentinvention, a circular nozzle plate 8 having a domed center portion 8 baround an annular base portion 8 a is set in a fuel injection nozzlepart of the valve, and a lower end part 3 b′ of a magnetic metal tube 3is arranged to surround circular nozzle plate 8. With this, a so-calledfuel holding recess “G” is produced which is defined by annular baseportion 8 a and lower end part 3 b′. The fuel holding recess “G” holds acertain amount of fuel by the force of a surface tension possessed bythe fuel. Fuel injection openings 8 c formed in domed center portion 8 bare constructed not to be covered with a fuel in fuel holding recess“G”. In other words, fuel holding recess “G” is positioned near thelower end part 3 b′ of magnetic metal tube 3 that is away from fuelinjection openings 8 c. Accordingly, possibility of having undesiredfuel composition deposit at the position of fuel injection openings 8 cis suppressed or at least minimized.

If the fuel injection valve 100 satisfies the above-mentioneddimensional condition (1), (2), (3) or (4) in the above-mentionedmanner, the valve 100 shows a satisfied performance in suppressingformation of the undesired fuel composition deposit.

Furthermore, if the fuel injection valve 100 satisfies all of theabove-mentioned dimensional conditions (1), (2), (3) and (4), the valve100 shows the best performance in suppressing formation of the undesiredfuel composition deposit.

Furthermore, due to the inherent construction of the circular nozzleplate 8 with the domed center portion 8 b, there is formed an annularrecess around the domed center portion 8 b, which can serve as acontainer for a small amount of residual fuel. This suppresses or atleast minimizes the possibility of having undesired fuel compositiondeposit on the peripheral area of fuel injection openings 8 c.

If desired, the following modifications may be used in the presentinvention.

In the above-mentioned embodiment 100, the lower end part 3 b′ is a partof the magnetic metal tube 3. However, if desired, a separate tubemember may be used in place of such lower end part 3 b′.

Furthermore, if desired, circular nozzle plate 8 may be formed on itslower surface with a plurality of radially extending grooves, eachextending between the peripheral portion of domed center portion 8 b andinner surface 3 c of lower end part 3 b′. Furthermore, the lower surfaceof circular nozzle plate 8 may be formed with a plurality of projectionsand recesses. With these measures, fuel containing capacity of fuelholding recess “G” is increased.

The entire contents of Japanese Patent Application 2005-056588 filedMar. 1, 2005 are incorporated herein by reference.

Although the invention has been described above with reference to theembodiment of the invention, the invention is not limited to suchembodiment as described above. Various modifications and variations ofsuch embodiment may be carried out by those skilled in the art, in lightof the above description.

1. A fuel injection valve comprising: a valve seat member having a valveseat with a fuel injection aperture; a valve body that is movablebetween a close position wherein the valve body is put on the valve seatand an open position wherein the valve body is separated from the valveseat; a biasing member that biases the valve body in a direction of theclose position; an electromagnetic coil that, upon energization, movesthe valve body in a direction of the open position against the biasingforce of the biasing member; a nozzle plate connected to the valve seatmember in a manner to cover the fuel injection aperture, the nozzleplate having at a part thereof facing the fuel injection aperture adomed portion that is projected away from the fuel injection aperture,the domed portion having a plurality of fuel injection openings; and aside wall that extends around and along a periphery of the nozzle plateso as to form a fuel holding recess that is defined by the nozzle plateother than domed portion and the side wall, the fuel holding recessbeing able to hold a certain amount of a fuel by the force of a surfacetension possessed by the fuel, wherein the nozzle plate is circular inshape and the side wall is cylindrical in shape, and in which the valveseat member is cylindrical in shape, and in which the cylindrical sidewall is a lower end part of a magnetic metal tube that surrounds thecylindrical valve seat member.
 2. A fuel injection valve as claimed inclaim 1 in which the domed portion of the nozzle plate is projected intoan enclosed space defined by the nozzle plate and the side wall.
 3. Afuel injection valve as claimed in claim 1, in which the magnetic metaltube constitutes a constructional base hollow member through which afuel flows.
 4. A fuel injection valve comprising: a valve seat memberhaving a valve seat with a fuel injection aperture; a valve body that ismovable between a close position wherein the valve body is put on thevalve seat and an open position wherein the valve body is separated fromthe valve seat; a biasing member that biases the valve body in adirection of the close position; an electromagnetic coil that, uponenergization, moves the valve body in a direction of the open positionagainst the biasing force of the biasing member; a nozzle plateconnected to the valve seat member in a manner to cover the fuelinjection aperture, the nozzle plate having at a part thereof facing thefuel injection aperture a domed portion that is projected away from thefuel injection aperture, the domed portion having a plurality of fuelinjection openings; and a side wall that extends around and along aperiphery of the nozzle plate so as to form a fuel holding recess thatis defined by the nozzle plate other than domed portion and the sidewall, the fuel holding recess being able to hold a certain amount of afuel by the force of a surface tension possessed by the fuel, whereinthe domed portion of the nozzle plate is projected into an enclosedspace defined by the nozzle plate and the side wall, and in which thefollowing inequalities are established in a dimensional condition:1.5 mm≦D1≦2.5 mm  (1) and0.1 mm≦h  (2) wherein: D1: diameter of the domed portion, h: height ofthe domed portion.
 5. A fuel injection valve as claimed in claim 4, inwhich the nozzle plate is circular in shape and the side wall iscylindrical in shape.
 6. A fuel injection valve as claimed in claim 4,in which the following inequality is established in a dimensionalcondition:(D2−D1)/2≧1.25 mm  (3) wherein: D2: inner diameter of the cylindricalside wall.
 7. A fuel injection valve as claimed in claim 6, in which thefollowing inequality is established in a dimensional condition:H≦2.0 mm  (4) wherein: H: height of the cylindrical side wall.